@article{8c83bfa644ba42b3bf04647c7ba0a0f5,
title = "Trajectory Estimation for Particles Observed in the Vicinity of (101955) Bennu",
abstract = "We analyze the trajectories of 313 particles seen in the near-Bennu environment between December 2018 and September 2019. Of these, 65% follow suborbital trajectories, 20% undergo more than one orbital revolution around the asteroid, and 15% directly escape on hyperbolic trajectories. The median lifetime of these particles is ∼6 hr. The trajectories are sensitive to Bennu's gravitational field, which allows us to reliably estimate the spherical harmonic coefficients through degree 8 and to resolve nonuniform mass distribution through degree 3. The particles are perturbed by solar radiation pressure, enabling effective area-to-mass ratios to be estimated. By assuming that particles are oblate ellipsoids of revolution, and incorporating photometric measurements, we find a median axis ratio of 0.27 and diameters for equivalent-volume spheres ranging from 0.22–6.1 cm, with median 0.74 cm. Our size distribution agrees well with that predicted for fragmentation due to diurnal thermal cycling. Detailed models of known accelerations do not produce a match to the observed trajectories, so we also estimate empirical accelerations. These accelerations appear to be related to mismodeling of radiation pressure, but we cannot rule out contributions from mass loss. Most ejections take place at local solar times in the afternoon and evening (12:00–24:00), although they occur at any time of day. We independently identify ten ejection events, some of which have previously been reported. We document a case where a particle ricocheted off the surface, revealing a coefficient of restitution 0.57±0.01 and demonstrating that some apparent ejections are not related to surface processes.",
author = "Chesley, {S. R.} and French, {A. S.} and Davis, {A. B.} and Jacobson, {R. A.} and M. Brozovi{\'c} and D. Farnocchia and S. Selznick and Liounis, {A. J.} and Hergenrother, {C. W.} and Moreau, {M. C.} and J. Pelgrift and E. Lessac-Chenen and Molaro, {J. L.} and Park, {R. S.} and B. Rozitis and Scheeres, {D. J.} and Y. Takahashi and D. Vokrouhlick{\'y} and Wolner, {C. W.V.} and C. Adam and Bos, {B. J.} and Christensen, {E. J.} and Emery, {J. P.} and Leonard, {J. M.} and McMahon, {J. W.} and Nolan, {M. C.} and Shelly, {F. C.} and Lauretta, {D. S.}",
note = "Funding Information: This material is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. This research was conducted in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. B. R. acknowledges funding support from the Royal Astronomical Society (RAS) and the U.K. Science and Technologies Facilities Council (STFC). The work of D.V. was partially funded by the Czech Science Foundation (Grant 18‐06083S). Special thanks to B. Semenov and the Navigation and Ancillary Information Facility (NAIF) team at JPL, who provided crucial support in our effort to fit the particle detections and analyze the associated results. We are grateful to H. Roper for her assistance in preparing the figures, and we thank M. Daly and M. Al Asad for sharing the off‐Bennu OLA detections. Finally, we thank the entire OSIRIS‐REx Team for making the encounter with Bennu possible. Funding Information: This material is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. This research was conducted in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. B.?R. acknowledges funding support from the Royal Astronomical Society (RAS) and the U.K. Science and Technologies Facilities Council (STFC). The work of D.V. was partially funded by the Czech Science Foundation (Grant 18-06083S). Special thanks to B. Semenov and the Navigation and Ancillary Information Facility (NAIF) team at JPL, who provided crucial support in our effort to fit the particle detections and analyze the associated results. We are grateful to H. Roper for her assistance in preparing the figures, and we thank M. Daly and M. Al Asad for sharing the off-Bennu OLA detections. Finally, we thank the entire OSIRIS-REx Team for making the encounter with Bennu possible. Publisher Copyright: {\textcopyright} 2020. The Authors.",
year = "2020",
month = sep,
day = "1",
doi = "10.1029/2019JE006363",
language = "English (US)",
volume = "125",
journal = "Journal of Geophysical Research: Planets",
issn = "2169-9097",
publisher = "Wiley-Blackwell Publishing Ltd",
number = "9",
}